Visible and near-IR spectroscopic and photochemical characterization of substituted metallophthalocyanines

Zinc Phthalocyanine Photochemistry by Raman Imaging, Fluorescence Spectroscopy and Femtosecond Spectroscopy in Normal and Cancerous Human Colon Tissues and Single Cells

Photodynamic therapy is a clinically approved alternative method for cancer treatment in which a combination of nontoxic drugs known as photosensitizers and oxygen is used. Despite intensive investigations and encouraging results, zinc phthalocyanines (ZnPcs) have not yet been approved as photosensitizers for clinical use. Label-free Raman imaging of nonfixed and unstained normal and cancerous colon human tissues and normal human CCD18-Co and cancerous CaCo-2 cell lines, without and after adding ZnPcS4 photosensitizer, was analyzed. The biochemical composition of normal and cancerous colon tissues and colon cells without and after adding ZnPcS4 at the subcellular level was determined. Analyzing the fluorescence/Raman signals of ZnPcS4, we found that in normal human colon tissue samples, in contrast to cancerous ones, there is a lower affinity to ZnPcS4 phthalocyanine. Moreover, a higher concentration in cancerous tissue was concomitant with a blue shift of the maximum peak position specific for the photosensitizer from 691-695 nm to 689 nm. Simultaneously for both types of samples, the signal was observed in the monomer region, confirming the excellent properties of ZnPcS4 for photo therapy (PDT). For colon cell experiments with a lower concentration of ZnPcS4 photosensitizer, c = 1 × 10-6 M, the phthalocyanine was localized in mitochondria/lipid structures; for a higher concentration, c = 9 × 10-6 M, localization inside the nucleus was predominant. Based on time-resolved experiments, we found that ZnPcS4 in the presence of biological interfaces features longer excited-state lifetime photosensitizers compared to the aqueous solution and bare ZnPcS4 film on CaF2 substrate, which is beneficial for application in PDT.

Photodynamic Opening of the Blood–Brain Barrier Using Different Photosensitizers in Mice

In a series of previous studies, we demonstrated that the photodynamic therapy (PDT), as a widely used tool for treatment of glioblastoma multiforme (GBM), also site-specifically opens the blood–brain barrier (BBB) in PDT-dose and age-related manner via reversible disorganization of the tight junction machinery. To develop the effective protocol of PDT-opening of the BBB, here we answer the question of what kind of photosensitizer (PS) is the most effective for the BBB opening. We studied the PDT-opening of the BBB in healthy mice using commercial photosensitizers (PSs) such as 5-aminolevulenic acid (5-ALA), aluminum phthalocyanine disulfonate (AlPcS), zinc phthalocyanine (ZnPc) and new synthetized PSs such as galactose functionalized ZnPc (GalZnPc). The spectrofluorimetric assay of Evans Blue albumin complex (EBAC) leakage and 3-D confocal imaging of FITC-dextran 70 kDa (FITCD) extravasation clearly shows a revisable and dose depended PDT-opening of the BBB to EBAC and FITCD associated with a decrease in presence of tight junction (TJ) in the vascular endothelium. The PDT effects on the BBB permeability, TJ expression and the fluorescent signal from the brain tissues are more pronounced in PDT-GalZnPc vs. PDT-5-ALA/AlPcS/ZnPc. These pre-clinical data are the first important informative platform for an optimization of the PDT protocol in the light of new knowledge about PDT-opening of the BBB for drug brain delivery and for the therapy of brain diseases.

Zinc(II) phthalocyanines as photosensitizers for antitumor photodynamic therapy

Photodynamic therapy (PDT) is a highly specific and clinically approved method for cancer treatment in which a nontoxic drug known as photosensitizer (PS) is administered to a patient. After selective tumor irradiation, an almost complete eradication of the tumor can be reached as a consequence of reactive oxygen species (ROS) generation, which not only damage tumor cells, but also lead to tumor-associated vasculature occlusion and the induction of an immune response. Despite exhaustive investigation and encouraging results, zinc(II) phthalocyanines (ZnPcs) have not been approved as PSs for clinical use yet. This review presents an overview on the physicochemical properties of ZnPcs and biological results obtained both in vitro and in more complex models, such as 3D cell cultures, chicken chorioallantoic membranes and tumor-bearing mice. Cell death pathways induced after PDT treatment with ZnPcs are discussed in each case. Finally, combined therapeutic strategies including ZnPcs and the currently available clinical trials are mentioned.

Photophysical Properties of Supported Dyes. Quantum Yield Calculations in Scattering Media

Aluminum tricarboximonoamidephthalocyanine and Rose Bengal were immobilized by adsorption and covalent linkage to different solid supports: silica, silanized silica, silanized silica modified with polylysine chains and NovaSyn® TG amino resin (low cross-linked polystyrene with polyethyleneglycol chains). Specially designed tools were used to evaluate absolute quantum yields in scattering media. A previously developed model was used to calculate fluorescence quantum yields in the solid state and a method is presented for the evaluation of singlet molecular oxygen quantum yields in suspensions. The method yields reliable results for dilute suspensions of particles with diameters much greater than the irradiation wavelength. Diffuse reflectance and, in the case of suspensions, total transmittance spectra are the basic inputs required. In this way the efficiencies of suspended solid photosensitizers were obtained for all samples and correlated with the dye concentration and the way of linking to the surface.

Effect of surface Fe2O3 clusters on the photocatalytic activity of TiO2 for phenol degradation in water

Surface modification of TiO(2) with Fe(2)O(3) clusters was made through chemisorption of ferric phthalocyaninetetracarboxylate onto TiO(2), followed by sintering in air to remove organic moiety. Solid characterization with electron paramagnetic resonance spectroscopy and other techniques showed that ferric oxides were highly dispersed on TiO(2) as a noncrystallized cluster, while TiO(2) phases remained unchanged. For phenol degradation in aerated aqueous suspension, only the sample containing less than 0.3 at.% Fe was more active than bare TiO(2) under UV light, whereas no activity was found under visible light. As anatase thermally transferred into rutile, the Fe-containing catalyst became less active than bare TiO(2), mainly ascribed to the increased size of Fe(2)O(3) clusters. In the presence of H(2)O(2), all Fe-containing catalysts were more active than bare TiO(2). Moreover, similar trend in activity among different catalysts was also observed with the formation of hydroxyl radicals, and with the generation of photocurrent measured under N(2) with Fe/TiO(2) electrode. Present work clearly shows that only Fe(2)O(3) clusters in a small size and at low coverage on TiO(2) are beneficial to the photocatalytic reaction, while excess iron oxide is detrimental. Possible mechanism is discussed in the text.

Effect of aggregation of a cationic phthalocyanine in micelles and in the presence of human serum albumin

The photophysical properties of tetrakis(1,1-dimethyl-2-trimethylammonium)ethylphthalocyaninato zinc(II) tetraiodide (I) – a water-soluble cationic phthalocyanine – are presented in the presence of human serum albumin (HSA) and in micelles of sodium dodecylsulfate ( SDS ) and hexadecyltrimethylammonium chloride ( CTAC ). Spectrophotometric measurements showed that the surfactants SDS and CTAC induce monomerization of I, although the latter less efficiently than the former. This effect is less pronounced in the presence of HSA. The strength of this effect is evaluated through dimerization constants, which are Kd = (5 ± 1) × 105 m−1 in SDS , (1.5 ± 0.5) × 106 M −1 in CTAC , and (1.8 ± 0.9) × 106 M −1 in HSA. Fluorescence experiments confirm that aggregation of I drops as the concentration of surfactant is raised. Triplet quantum yields also decreased upon aggregation and were Φ T = 0.59, 0.16, and < 0.01 in SDS , CTAC , and HSA, respectively. These results indicate that the affinity of I for the environment is not just due to ionic interactions; hydrophobic interactions play an equally important role.

Photophysical properties of microencapsulated phthalocyanines

Lipophilic substituted zinc(II) phthalocyanines: 2,3,9,10,16,17,23,24-octakis[(N,N-dimethylaminoethylsulfanyl)]phthalocyaninatozinc(II) (S1) and tetrakis(N,N-dibutylaminoethoxy)phthalocyaninatozinc(II) (3) were incorporated into soybean L-α-phosphatidylcholine (SPC) liposomes of 100 nm diameter. Liposomes were characterized by static light scattering (SLS), transmission electronic microscopy (TEM), and differential scanning calorimetry. The fluorescence quantum yield and singlet molecular oxygen production of 3 are Φ F = 0.15 and ΦΔ = 0.24, respectively, whereas the same photophysical parameters for S1 are Φ F = 0.13 and ΦΔ = 0.51. Higher values of Φ F and ΦΔ are obtained in organic solvent for both dyes. Synthesis of compound 3 has also been reported.

Long wavelength absorbing cationic Zn(II)-phthalocyanines as fluorescent contrast agents for B16 pigmented melanoma

Three cationic zinc phthalocyanines ( ZnPcs ), tetrakis-(3-methylpyridyloxy)-, tetrakis-(3-hexyl-pyridyloxy)-, and tetrakis-(3-dodecylpyridyloxy)phthalocyaninezinc ( ZnPc Me, ZnPc He and ZnPc Do) have been studied as advanced fluorescent contrast agents for pigmented melanoma tumor. UV-vis spectroscopic properties of the monomers were investigated. Their photophysical behavior as a substantial part of dye-induced fluorescence was evaluated. The selective accumulation and labeling capacity towards B16F0 pigmented melanoma tumor were determined. Melanin containing cells were isolated and incubated with ZnPcs at several time intervals (1, 1.5 and 6 h) following the kinetics of cellular uptake. The highest accumulation was found for ZnPcHe . A lower uptake was detected for the more lipophilic ZnPcDo and more hydrophilic ZnPcMe . The fluorescence diagnostic potential of ZnPcs towards pigmented melanoma by using an argon-dye laser detection set-up was demonstrated.

A synthetic approach towards novel octa-substituted zinc(II) phthalocyanines with different solubility and photophysical properties

The synthesis and behavior in homogeneous solutions of 2,3,9,10,16,17,23,24-octakis(3-phthalimidopropyloxy)phthalocyaninatozinc(II) (5) and 2,3,9,10,16,17,23,24-octakis(3-aminopropyloxy)phthalocyaninatozinc(II) (6) are reported.

Photophysical properties of Zn(II) phthalocyaninates incorporated into liposomes

Amphiphilic phthalocyanines are used as potential photosensitizers in photodynamic therapy. The low water solubility of most of these dyes is the reason that different kinds of vehicles are employed as endogenous carriers. Due to the photophysical inactivity of the phthalocyanine aggregates, it is important to improve their solubility in order to study dyes in solid tumor models. On the other hand, the photodynamic therapy activity depends on the location of phthalocyanines in the cell and the interaction of cellular components. In this work, the photophysical properties of tetrasubstituted Zn ( II ) phthalocyanines with different lipophilic properties are incorporated into liposomes of L-α-dimyristoylphosphatidylcholine (DMPC). The fluorescence quantum yields, the association constants and their localization in the membranes are reported.

Excited state dynamics of zinc and aluminum phthalocyanine carboxylates

Photophysical parameters for zinc and aluminium tetracarboxylphthalocyanines (ZnTCPc and AlTCPc, respectively) and their octacarboxy substituted counterparts (ZnOCPc and AlOCPc) were studied. Data for the fluorescence quenching of the complexes by benzoquinone (BQ) were treated using the Stern-Volmer analysis, and the quenching was found to follow a diffusion-controlled (dynamic) bimolecular mechanism. Theoretical values of bimolecular rate constant for complex-BQ interactions were determined using the Stokes-Einstein-Smoluchowski model; and the values, together with the Stern-Volmer quenching constants were used in calculating the fluorescence lifetimes of the complexes. The thermodynamics of the MPc-BQ interaction, in terms of solvent reorientation energy is also discussed.

Photodynamic ultradeformable liposomes: Design and characterization

Hydrophobic ([tetrakis(2,4-dimetil-3-pentyloxi)-phthalocyaninate]zinc(II)) (ZnPc) and hydrophilic ([tetrakis(N,N,N-trimethylammoniumetoxi)-phthalocyaninate]zinc(II) tetraiodide) (ZnPcMet) phthalocyanines were synthesized and loaded in ultradeformable liposomes (UDL) of soybean phosphatidylcholine and sodium cholate (6:1, w/w, ratio), resulting 100 nm mean size vesicles of negative Zeta potential, with encapsulation efficiencies of 85 and 53%, enthalpy of phase transition of 5.33 and 158 J/mmol for ZnPc and ZnPcMet, respectively, indicating their deep and moderate partition into UD matrices. Matrix elasticity of UDL-phthalocyanines resulted 28-fold greater than that of non-UDL, leaking only 25% of its inner aqueous content after passage through a nanoporous barrier versus 100% leakage for non-UDL. UDL-ZnPc made ZnPc soluble in aqueous buffer while kept the monomeric state, rendering singlet oxygen quantum yield (Phi(Delta)) similar to that obtained in ethanol (0.61), whereas UDL-ZnPcMet had a four-fold higher Phi(Delta) than that of free ZnPcMet (0.21). Free phthalocyanines were non-toxic at 1 and 10 microM, both in dark or upon irradiation at 15 J/cm2 on Vero and J-774 cells (MTT assay). Only liposomal ZnPc at 10 microM was toxic for J-774 cells under both conditions. Additionally, endo-lysosomal confinement of the HPTS dye was kept after irradiation at 15 J/cm2 in the presence of UDL-phtalocyanines. This could lead to improve effects of singlet oxygen against intra-vesicular pathogen targets inside the endo-lysosomal system.

Photophysics on surfaces: determination of absolute fluorescence quantum yields from reflectance spectra

A method for the calculation of absolute fluorescence quantum yields for dyes attached to solid particles based on reflectance measurements is reported. The same procedure allows calculation of true reflectance spectra (free of fluorescence) for highly fluorescent materials as well. Samples ofcresyl violet were immobilized by adsorption on microgranular cellulose in the concentration range 4.5 x 10(-9) to 3.8 x 10(-6) mol g(-1). Diffuse and total reflectance spectra were recorded with and without insertion of an optical absorption filter between the output of the integrating sphere of a reflectance spectrometer and the photodetector in order to block fluorescence partially. From these data, the relative emission spectrum of the dye, the filter transmission spectrum, and the detector sensitivity, true reflectances and absolute fluorescence quantum yields were recovered. Observed fluorescence quantum yields, affected by dye aggregation and inner filter effects, were concentration and wavelength dependent, ranging approximately between 0.1 and 0.6. The analysis of remission function spectra showed that dye aggregation is negligible up to a concentration of 1.41 x 10(-7) mol g(-1). Fluorescence data were corrected for reemission and reabsorption using a suitable model [Lagorio, M. G.; Dicelio, L. E.; Litter, M. I.; San Roman, E. J. Chem. Soc., Faraday Trans. 1998, 94, 419]. Application of this model to samples showing no aggregation yielded a wavelength-independent true fluorescence quantum yield of 0.60 +/- 0.05, similar to values found in solution. The usage of cresyl violet as a reference for the evaluation of fluorescence quantum yields for weakly fluorescing samples in the solid phase is discussed.

A comparative study of the photophysical and phototoxic properties of octakis(decyloxy)phthalocyaninato zinc(ii), incorporated in a hydrophilic polymer, in liposomes and in non-ionic micelles

Factors such as charge, aggregation and lipophilicity influence photosensitiser localisation. The lipophilic octasubstituted sensitiser 2,3,9,10,16,17,23,24-octakis(decyloxy)phthalocyaninato zinc(II) was incorporated into liposomes of dimyristoyl-L-alpha-phosphatidylcholine (DMPC), non-ionic micelles of Tween 80 and the hydrosoluble polymer Solutol HS 15 in order to investigate how these different environments affect the photophysical properties and phototoxicity of the photosensitiser. Fluorescence quantum yields and singlet molecular oxygen generation are enhanced in the presence of Solutol HS 15. Phototoxicities were calculated by employing a concentration of 10(-7) M of the dye against the Hep-2 cell line, which showed a viability of 53 and 30% in DMPC and Solutol HS 15, respectively. After 24 h of photodynamic therapy with 15 min irradiation, apoptotic and necrotic cells were observed.

Observation of a fluorescent dimer of a sulfonated phthalocyanine

With very few exceptions, phthalocyanine dimers are found to be nonfluorescent. We report here the observation of a fluorescent dimer of a tetrasulfonated copper phthalocyanine in ethanol and water. Fluorescence excitation and emission spectra at room temperature and at 77 K are presented. These are consistent with the conventional model of exciton coupling in a cofacial dimer.

Synthesis and photophysical properties of a new cationic water-soluble Zn phthalocyanine

The synthesis of tetrakis (1,1-dimethyl-2-trimethylammonium)ethylphthalocyaninato Zn(II) tetraiodide 2--a new cationic phthalocyanine--is reported as well as its photophysical properties in water, relevant for the use of this dye as photodynamic sensitizer. The hydrophobicity of the macrocycle leads to strong aggregation which lowers the fluorescence and singlet oxygen quantum yields of aqueous solutions of 2. Photophysical parameters agree with those of other Zn phthalocyanines when correction is performed for the fraction of light absorbed by the monomer.